Acid generation efficiency prediction by bond cleavage calculation of EUV photoacid generators

Abstract

For designing high-resolution integrated circuits, extreme ultraviolet (EUV) lithography using 13.5-nm light is indispensable; however, stochastic issues which can result in pattern roughness and stochastic defects have yet to be resolved. Many of these issues can relate to the low photon density when compared to DUV lithography. To resolve stochastic concerns in chemically amplified (CA) photoresists, it is important to use appropriate photoacid generator (PAG). EUV PAGs are designed to capture secondary electrons that originate from EUV irradiation to the photoresists. Herein, we focused on in silico analysis of C-S bond cleavage of sulfonium cation series, which is a well-known mechanism in production of photogenerated acids. Change in cation types or substituted functional groups directly affect electron affinities of PAG cations, as well as the efficiency of C-S bond cleavage reaction. Finally, the correlation between actual lithographic performance and calculated properties was carried out to understand the factors that influence efficiency of photoacid generation.